Display device, brightness adjustment device, method of adjusting brightness, and program

ABSTRACT

Provided is a display device including a setting condition acquisition unit for obtaining various conditions for adjusting a gain of a video-signal, a current-brightness table calculation unit that calculates a table representing a relationship between an average brightness and a gain of a video-signal, and that calculates the table capable of setting a peak-brightness and power consumption of the video-signal independently, based on the various conditions acquired by the setting condition acquisition unit, a video-average brightness conversion block that calculates average-brightness of the video-signal input for each frame, a current-brightness control table that calculates a gain of the video-signal from the table based on the average-brightness calculated above, a video gain block that adjusts the video-signal using the gain calculated above, and a display panel that includes a plurality of pixels that emit light in response to a video-signal and displays a video based on the video-signal adjusted above.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/131,617, filed May 27, 2011, which is a National Stage ofPCT/JP2009/070252, filed Dec. 2, 2009 and claims the benefit of priorityunder 35 U.S.C. §119 of Japanese Application No. 2008-316291, filed Dec.30, 2009. The entire contents of each of which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a display device, a brightnessadjustment device, a method of adjusting brightness, and a program.

BACKGROUND ART

Conventionally, as a flat thin display device, a liquid crystal displaydevice using a liquid crystal, a plasma display device using plasma, andthe like have been put into practical use.

The liquid crystal display device is a display device in which abacklight device is installed, and an image is displayed such that whena voltage is applied, an arrangement of liquid crystal molecules changesto pass or block light from the backlight. The plasma display device isa display device that displays an image such that a voltage is appliedto a gas sealed in a substrate to create a plasma state, and ultravioletlight generated by energy generated when an original state is returnedfrom the plasma state is irradiated to a phosphor and thus converted tovisible light.

Meanwhile, in recent years, a light-emitting type display device usingan organic electroluminescence (EL) device in which a device itselfemits light when a voltage is applied has been developed. The organic ELdevice changes from a ground state to an excited state when energy isreceived by electrolysis and emits energy of a difference as light whenthe ground state is returned from the excited state. An organic ELdisplay device displays an image using light emitted from the organic ELdevice.

Unlike the liquid crystal display device that requires the backlight,the light-emitting type display device does not require the backlightsince the device emits light by itself. Thus, the light-emitting typedisplay device can be configured thinner than the liquid crystal displaydevice. Further, compared to the liquid crystal display device, theorganic EL display device is excellent in a moving image characteristic,a viewing angle characteristic, color reproducibility, and the like andthus has attracted attention as a next generation flat thin displaydevice.

In this circumstance, for example, as stated in the following PatentLiterature 1, in a light-emitting type display device such as an organicEL display, a technique of reducing an electric current flowing throughthe panel to less than a maximum current and reducing peak brightnessbased on information of a video signal from a panel protectionstandpoint has been known.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No.2007-147868.

SUMMARY OF INVENTION Technical Problem

In the above conventional technique, however, in order to reduce powerconsumption, a current value is reduced to less than a maximum current,and peak brightness is reduced. Therefore, although reducing powerconsumption is possible, it is difficult for a user to set flexiblyaccording to situation, such as to adjust brightness in a case wheremovie is dark, to reduce only power consumption, or to keep brightnesswhile reducing power to some extent, or the like. In addition, it wasnot possible to adjust balancing the power consumption and the peakbrightness in accordance with brightness of a room.

Further, in a case where a system uses a surface light source such as aliquid crystal display, in order to reduce the power consumption, tobrighten movie signals while reducing brightness of a backlight.However, in this case, information that the movie signals originallyhave, such as, texture, gloss, or contrast, or the like, would be lost.

The present invention is made in view of the above-mentioned issue, andaims to provide a display device, a brightness adjustment device, amethod of adjusting brightness, and a program which are novel andimproved, and which are capable of providing optimum movie in accordancewith a situation by adjusting a peak brightness and power consumptionindependently.

Solution to Problem

According to an aspect of the present invention, in order to achieve theabove-mentioned object, there is provided a display device including asetting condition acquisition unit for acquiring various conditions foradjusting a gain of a video signal, a table calculation unit thatcalculates a table representing a relationship between an averagebrightness and a gain of a video signal, and that calculates the tablecapable of setting a peak brightness and power consumption of the videosignal independently, based on the various conditions acquired by thesetting condition acquisition unit, an average brightness calculationunit that calculates an average brightness of a video signal input foreach frame, a gain calculation unit that calculates a gain of a videosignal from the table based on the average brightness calculated by theaverage brightness calculation unit, a video signal adjustment unit thatadjusts a video signal using the gain calculated by the gain calculationunit, and a display panel that includes a plurality of pixels that emitlight in response to a video signal and displays a video based on thevideo signal adjusted by the video signal adjustment unit.

According to the above configuration, various conditions for adjusting again of a video signal is acquired, based on the acquired variouscondition, a table representing a relationship between an averagebrightness and a gain of a video signal is calculated. This table isassumed to be a table being set with a peak brightness and powerconsumption of the video signal independently. The peak brightness ofthe video signal input for each frame is calculated, and the gain of thevideo signal is calculated from the table based on the calculatedaverage brightness. The video signal is adjusted using the gaincalculated by the gain calculation unit, and a video is to be displayedbased on the adjusted video signal on a display panel included aplurality of pixels that emit light in response to a video signal. Sinceit becomes possible to control the peak brightness and power consumptionindependently in accordance with various conditions, the powerconsumption can be reduced in a state in which contrast feelingoriginally included in the video signal, a gloss of an object or a humanskin, or the like is all maintained. Further, optimum video expressioncan be made according to the user's viewing environment. Thus, the videocan be displayed at optimum brightness and power consumption accordingto the various conditions.

Further, the setting condition acquisition unit may acquire the variousconditions including environmental information indicating an environmentsurrounding the display device, user setting information set by a user,information on maximum power consumption that the display panel allows,or information on meta data indicating a category of a video.

Further, it may further include a memory attached to a front stage ofthe video signal adjustment unit, the memory which holds temporarily avideo signal of a frame by which a gain is multiplied.

Further, it may further include a chromaticity calculation unit forcalculating chromaticity of a video signal based on the variousconditions acquired by the setting condition acquisition unit, and achromaticity adjustment unit for adjusting the chromaticity of the videosignal using the chromaticity calculated by the chromaticity calculationunit.

According to another aspect of the present invention, in order toachieve the above-mentioned object, there is provided a brightnessadjustment device including a setting condition acquisition unit foracquiring various conditions for adjusting a gain of a video signal, atable calculation unit that calculates a table representing arelationship between an average brightness and a gain of a video signal,and that calculates the table capable of setting a peak brightness andpower consumption of the video signal independently, based on thevarious conditions acquired by the setting condition acquisition unit,an average brightness calculation unit that calculates an averagebrightness of a video signal input for each frame, a gain calculationunit that calculates a gain of a video signal from the table based onthe average brightness calculated by the average brightness calculationunit, and a video signal adjustment unit that adjusts a video signalusing the gain calculated by the gain calculation unit.

Further, the setting condition acquisition unit may acquire the variousconditions including environmental information indicating an environmentsurrounding the display device, user setting information set by a user,information on maximum power consumption that the display panel allows,or information on meta data indicating a category of a video.

Further, it may further include a memory attached to a front stage ofthe video signal adjustment unit, the memory which holds temporarily avideo signal of a frame by which a gain is multiplied.

Further, it may further include a chromaticity calculation unit forcalculating chromaticity of a video signal based on the variousconditions acquired by the setting condition acquisition unit, and achromaticity adjustment unit for adjusting chromaticity of a videosignal using the chromaticity calculated by the chromaticity calculationunit.

According to another aspect of the present invention, in order toachieve the above-mentioned object, there is provided a method ofadjusting brightness including the steps of acquiring various conditionsfor adjusting a gain of a video signal, calculating a table representinga relationship between an average brightness and a gain of a videosignal, and calculating the table capable of setting a peak brightnessand power consumption of the video signal independently, based on thevarious conditions acquired by the setting condition acquisition unit,calculating an average brightness of a video signal input for eachframe, calculating a gain of a video signal from the table based on thecalculated average brightness, and adjusting a video signal using thegain calculated by the gain calculation unit.

According to another aspect of the present invention, in order toachieve the above-mentioned object, there is provided a program causinga computer to execute the steps of acquiring various conditions foradjusting a gain of a video signal, calculating a table representing arelationship between an average brightness and a gain of a video signal,and calculating the table capable of setting a peak brightness and powerconsumption of the video signal independently, based on the variousconditions acquired by the setting condition acquisition unit,calculating an average brightness of a video signal input for eachframe, calculating a gain of a video signal from the table based on thecalculated average brightness, and adjusting a video signal using thegain calculated by the gain calculation unit.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a displaydevice, a brightness adjustment device, a method of adjustingbrightness, and a program which are capable of providing optimum moviein accordance with a situation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of a displaydevice according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating an example of a tableretained in a current-brightness control table.

FIG. 3 is a schematic diagram illustrating a technique of controlling apeak brightness and power consumption, respectively, in a characteristicof a solid line of FIG. 2.

FIG. 4 is a schematic diagram illustrating a technique of controlling apeak brightness and power consumption, respectively, in a characteristicof a solid line of FIG. 2.

FIG. 5 is a schematic diagram illustrating an example of a configurationof a current-brightness table calculation unit.

FIG. 6 is a schematic diagram illustrating a specific configuration of achromaticity calculation unit.

FIG. 7 is a flowchart illustrating a process performed by a brightnessadjustment device.

FIG. 8 is a functional block diagram illustrating a configuration of adisplay device including a backlight device.

FIG. 9 is a schematic diagram illustrating a configuration of abacklight device that includes a light source control unit and a surfacelight source.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted. Further, a description willbe made in the following order.

1. Configuration of Display Device According to Embodiment of PresentInvention

2. Example of Table Retained in Current-Brightness Control Table

3. Various Information for Setting Video Gain

4. Technique of Controlling Peak Brightness and Power Consumption

5. Example of Configuration of Current-Brightness Table Calculation Unit

6. Configuration for Adjusting chromaticity of Movie Signals

7. Process Procedure of Method of Adjusting Brightness

8. Application of Backlight Device.

[1. Configuration of Display Device According to Embodiment of PresentInvention]

FIG. 1 is a schematic diagram illustrating a configuration of a displaydevice 200 according to an embodiment of the present invention. Forexample, the display device 200 is a device such as a television set anddisplays a television program based on a video signal obtained from abroadcast wave. The display device 200 includes a brightness adjustmentdevice 100 and a display panel 300. The video signal is input to thebrightness adjustment device 100 where brightness is adjusted and thentransmitted to the display panel 300. The display panel 300 displays avideo based on the adjusted video signal.

In the present embodiment, the display device 300 is configured with alight-emitting type panel. In the present embodiment, an organic ELpanel is described as the display panel 300. The display panel 300receives the video signal whose brightness is adjusted, causes anorganic EL device that is an example of a light-emitting device to emitlight in response to an input signal and pulse, and displays a movingimage or a still image. A surface of the display panel 300 fordisplaying an image has a flat shape. The organic EL device is alight-emitting type device that emits light when a voltage is applied,and a light emission amount is in proportion to a voltage. Thus, an ILcharacteristic (a current-light emission amount characteristic) of theorganic EL device also has a proportional relationship.

If the video signal is supplied, the display device 100 displays a videothrough the display panel 300 by lighting up pixels arranged inside thedisplay panel 300 according to the video signal. In the display panel300, a scan line for selecting a pixel at a predetermined scan period, adata line for providing brightness information for driving a pixel, anda pixel circuit for controlling a current amount based on the brightnessinformation and causing the organic EL device, which is thelight-emitting device, to emit light according to the current amount arearranged in the form of a matrix. The scan line, the data line, and thepixel circuit are configured as described above, and thus the displaypanel 300 can display the video according to the video signal.

As illustrated in FIG. 1, the brightness adjustment device 100 includesa video signal memory 102, a video gain block 104, a video-averagebrightness conversion block 106, and a setting condition acquisitionunit 108. The setting condition acquisition unit 108 acquires a settingcondition such as peak brightness (maximum value of brightness)information, power consumption information, environment information, orthe like. The brightness adjustment device 100 further includes acurrent-brightness control table 110, a current-brightness tablecalculation unit 112, and a chromaticity calculation unit 114, and achromaticity setting unit 116. Each of the functional blocks illustratedin FIG. 1 may be configured by hardware (a circuit) or an arithmeticprocessing unit (CPU) and software (a program) for causing it tofunction. When each functional block is configured by the arithmeticprocessing unit and the software, the program may be stored in a memoryincluded in the display device 200 or a recording medium such as amemory inserted from the outside. For example, the setting conditionacquisition unit 110 and the current-brightness table calculation unit112 may be configured by the arithmetic processing unit and the softwarefor causing it to function, and the other functional blocks may beconfigured by hardware.

The brightness adjustment device 100 receives the video signal fordisplaying the video on the display panel 300. Here, if it is assumedthat the moving image is displayed on the display panel 300, the videosignal is input for each frame of the moving image. The brightnessadjustment device 100 performs brightness adjustment on the video signalof each frame through the video gain block 104, performs chromaticityadjustment in the chromaticity setting unit 116, and transmits the videosignal done with these adjustments to the display panel 300.

Hereinafter, each of the functional blocks of the brightness adjustmentdevice 100 illustrated in FIG. 1 will be described. The video signalmemory 102 may be configured with a typical frame memory and temporarilystore the video signal that is input for each frame. The video-averagebrightness conversion block 104 calculates an average brightness of eachframe by averaging brightness of all pixels on the video signal of eachframe. The calculated average brightness is transmitted to thecurrent-brightness control table 110. The video signal is transmitted tothe video gain block 104 for each frame.

The video-average brightness conversion block 104 calculates an electriccurrent flowing through the display panel 300. In a device such as anorganic EL panel or a light-emitting diode (LED) display, since anelectric current and brightness are uniquely decided by a linearrelationship, it is possible to easily calculate a consumption currentbased on brightness of the video signal stored in the video signalmemory 102, a color difference signal, and R, G, and B signals.

The current-brightness control table 110 retains a table in which arelationship between an average brightness and a video gain is defined.The current-brightness control table 110 is a table for converting again amount by which the video signal is multiplied from an averagebrightness (an average video signal level) obtained from the videosignal for controlling a maximum brightness or a current value basedthereon. As will be described later, this table is created by thecurrent-brightness table calculation unit 112 according to variousconditions. The current-brightness control table 110 calculates thevideo gain based on the average brightness transmitted from thevideo-average brightness conversion block 104 or the current value byusing the table. The calculated video gain is transmitted to the videogain block 104.

The video gain block 104 multiplies the corresponding video signal inputfrom the video signal memory 102 by the video gain calculated by thecurrent-brightness control table 110. As a result, the brightness of thevideo signal is optimally adjusted. As described above, in the presentembodiment, by temporarily retaining the video signal in the videosignal memory 102, a video signal of a certain frame can be adjustedusing a video gain calculated based on an average brightness of theframe.

Further, in a case in which it is configured to adjust a video signal ofthe next or later frame using the calculated video gain, the videosignal memory 102 may not be installed, and the input video signal canbe input directly to the video gain block 104 and the video-brightnessconversion block 106. In this case, it is preferable to have anovercurrent control function for protecting the display panel 300.

[2. Example of Table Retained in Current-Brightness Control Table]

FIG. 2 is a characteristic diagram illustrating an example of a tableretained in the current-brightness control table 110. A horizontal axisdenotes an average brightness of a video, and a vertical axis denotes avideo gain.

In FIG. 2, a characteristic indicated by a solid line represents arelationship between a video average brightness and a video gain createdby the current-brightness table calculation unit 112 according tovarious conditions. This characteristic is basically set so that if anaverage brightness increases, a video gain decreases. Thus, when a videois bright and an average brightness is high, a video gain is set to asmall value. Further, when a video is dark and an average brightness islow, a video gain is set to a large value.

In FIG. 2, a characteristic indicated by a dotted line represents amaximum value of power consumption of the display panel 300, and thischaracteristic is previously determined based on a characteristic of thedisplay panel 300. By making the characteristic of the averagebrightness and the video gain indicated by the solid line equal to orless than the characteristic of the dotted line, the power consumptionof the display panel 300 can be equal to or less than the maximum value,deterioration of the display panel 300 can be prevented, and powerconsumption can be reduced.

In the present embodiment, the characteristic of the solid lineillustrated in FIG. 2 is rewritten at a predetermined time interval andset on a case-by-case basis, according to various conditions such asinformation of peak brightness (peak information), information set bythe user, power consumption information, and environment information.The setting condition acquisition unit 108 has a function of acquiringthe various conditions.

[3. Various Information for Setting Video Gain]

Hereinafter, the various information acquired by the setting conditionacquisition unit 108 will be described. The information of peakbrightness is a condition for setting a maximum brightness in thecharacteristic of the solid line in FIG. 2. The information of peakbrightness is mainly decided by information set by the user (user-setinformation) and environment information (information such as thetemperature, humidity, lightness, and color temperature of a place wherethe display device 200 is placed).

The user-set information is set by the user operating an operationbutton (not shown) of the display device 200 and includes informationsuch as brightness of a video, a contrast, power consumption (a normalmode or a power save mode), and an image quality mode. The user can setthe information to a desired value by operating the operation button.

For example, when the user performs setting for reducing brightnessthrough the user-set information, the characteristic of the solid lineof FIG. 2 is set by the current-brightness table calculation unit 112 sothat the peak brightness can decrease. In this case, the characteristicof the solid line of FIG. 2 changes so that the maximum value of thevideo gain can further decrease.

The display device 200 may include a temperature sensor, a humiditysensor, a brightness sensor, a color difference sensor, or the like foracquiring the environment information, and the environment informationmay be acquired from the sensors. Alternatively, the environmentinformation may be acquired from a predetermined database 400. In thiscase, the database 400 and the brightness adjustment device 100 may beconnected via a network such as the Internet 500.

For example, when it is judged by the brightness sensor that externallight of a place where the display device 200 is placed is bright, thecurrent-brightness table calculation unit 112 sets the characteristic ofthe solid line of FIG. 2 so that the peak brightness can furtherincrease. As a result, even in a bright room, a video that is easy for aviewer to watch can be displayed on the display panel 300.

The video signal is also input to the setting condition acquisition unit108. When it is judged, based on an average value of the video signal orthe like, that the brightness of the video is high, thecurrent-brightness table calculation unit 112 sets the characteristic ofthe solid line of FIG. 2 so that the peak brightness can decrease. As aresult, it is possible to prevent the viewer from experiencing glare.

The power consumption information is information corresponding to thecharacteristic of the dotted line of FIG. 2 and is previously decidedaccording to a characteristic of the display panel 300. Thecurrent-brightness table calculation unit 112 sets the characteristic ofthe average brightness and the video gain indicated by the solid to beequal to or less than the characteristic of the dotted line. As aresult, panel power consumption can be prevented from exceeding anallowable range, and deterioration of the display panel can besuppressed. Further, it is possible to minimize power consumption of thedisplay device 200. If the characteristic indicated by the solid lineexceeds the characteristic of the dotted line, the current-brightnesstable calculation unit 112 sets the characteristic of the solid line tooverlap with the characteristic of the dotted line on the exceededportion. As a result, it is possible to reliably prevent the powerconsumption from exceeding the allowable range.

The setting condition acquisition unit 108 acquires various metadata asthe other information. For example, the metadata is information acquiredfrom the video signal and includes information such as a genre of avideo (a news program, a drama, a movie, etc.), a title of a video, anda current weather (when a video is a weather forecast). The variousmetadata may be acquired from the database 400.

When it is detected, based on the metadata acquired from the videosignal or the database 400, that a video is a variety program, thecurrent-brightness table calculation unit 112 sets the characteristic sothat the peak brightness can decrease. As a result, when a programhaving a relatively high average brightness such as a variety program isbroadcast, it is possible to prevent the viewer from experiencingexcessive glare. For example, even when a video of a starry sky isdisplayed, a video of a clearer starry sky can be provided by increasingthe peak brightness.

The current-brightness table calculation unit 112 performs a calculationbased on the various setting conditions acquired by the settingcondition acquisition unit 108 and sets the characteristic indicated bythe solid line of FIG. 2. For example, when it is detected by the sensorfor acquiring the above described environment information that externallight brightness of a place where the display device 200 is placed ishigh, the characteristic of the solid line of FIG. 2 is set so that thepeak brightness can further increase. In a case in which setting ofreducing power consumption is performed, for example, when the user setsan energy save mode, the characteristic of the solid line of FIG. 2 isset so that power consumption can further decrease.

[4. Technique of Controlling Peak Brightness and Power Consumption]

FIGS. 3 and 4 are schematic diagrams illustrating a technique ofcontrolling the peak brightness and the power consumption, respectively,in the characteristic of the solid line of FIG. 2. FIG. 3 illustrates atechnique of controlling the peak brightness, and FIG. 4 illustrates atechnique of controlling the power consumption.

As illustrated in FIG. 3, in the case of controlling the peakbrightness, only the peak brightness is controlled by changing thecharacteristic in a direction indicated by an arrow of FIG. 3 in a statein which the power consumption is kept. Meanwhile, as illustrated inFIG. 4, in the case of controlling the power consumption, only powerconsumption is controlled by changing the characteristic in a directionindicated by an arrow of FIG. 4 in a state in which the peak brightnessis kept. By controlling the peak brightness and the power consumptionthrough the techniques illustrated in FIGS. 3 and 4 as described above,the peak brightness and the power consumption can be individuallycontrolled.

Thus, according to the present embodiment, by individually controllingthe peak brightness and the power consumption in a range that does notexceed the characteristic of the dotted line of FIG. 2, the brightnessof the video signal can optimally be adjusted in a range equal to orless than maximum power consumption allowed by the display panel 300.

The calculation by the current-brightness table calculation unit 112 isperformed, for example, at an interval of 200 [ms] to 1 [s], and thecharacteristic of the table indicated by the solid line of FIG. 2 isrewritten on a case-by-case basis. The characteristic may be rewrittenfor each frame.

[5. Example of Configuration of Current-Brightness Table CalculationUnit]

FIG. 5 is a schematic diagram illustrating an example of a configurationof the current-brightness table calculation unit 112. As illustrated inFIG. 5, the current-brightness table calculation unit 112 includes anexternal light coefficient setting unit 112 a, a temperature coefficientsetting unit 112 b, a chromaticity coefficient setting unit 112 c, agenre table 112 d, a user coefficient setting unit 112 e, and acurrent-brightness table calculation unit 112 f. The external lightcoefficient setting unit 112 a sets a coefficient based on brightness ofexternal light input as the environment information. The temperaturecoefficient setting unit 112 b sets a coefficient based on thetemperature input as the environment information. The chromaticitycoefficient setting unit 112 c sets a coefficient based on chromaticityinput as the environment information. The genre table 112 d sets acoefficient based on a genre of a video input as metadata. The usercoefficient setting unit 112 e sets a coefficient based on a settingvalue set by the user.

The current-brightness table calculation unit 112 f calculates thecharacteristic of the solid line illustrated in FIG. 2 based on thecoefficients set by the external light coefficient setting unit 112 a,the temperature coefficient setting unit 112 b, the chromaticitycoefficient setting unit 112 c, the genre table 112 d, and the usercoefficient setting unit 112 e.

As described above, according to the brightness adjustment device 100 ofthe present embodiment, it is possible to individually control the peakbrightness and the power consumption in the current-brightnessadjustment table according to the various conditions. As a result, thepower consumption can be reduced in a state in which contrast feelingoriginally included in the video signal, a gloss of an object or a humanskin, or the like is all maintained. Further, optimum video expressioncan be made according to the user's viewing environment. Thus, the videocan be displayed at optimum brightness and power consumption accordingto the various conditions.

[6. Operation of Flash Control Calculation Unit]

Next, in the brightness adjustment device 100, the chromaticitycalculation unit 114 and the chromaticity setting unit will bedescribed. The chromaticity calculation unit calculates an optimalchromaticity for movie signals in each frame in accordance with eachsetting condition acquired in the setting condition acquisition unit108, and sends them to the chromaticity setting unit 116. Thechromaticity setting unit 116 sets chromaticity of the movie signalsbased on the chromaticity calculated in the chromaticity calculationunit 114. The movie signals set with chromaticity in the chromaticitysetting unit 116 are sent to the display panel 300. Here, chromaticityis a concept including color temperature, and the chromaticity settingunit 116 also adjusts tone of R, G, B as well as adjusting the colortemperature of movie data.

FIG. 6 is a schematic diagram illustrating a specific configuration ofthe chromaticity calculation unit 114. As illustrated in FIG. 6, thechromaticity calculation unit 114 includes an external light coefficientsetting unit 114 a, a temperature coefficient setting unit 114 b, achromaticity coefficient setting unit 114 c, a genre table 114 d, a usercoefficient setting unit 114 e, and a chromaticity calculation unit 114f. The external light coefficient setting unit 114 a sets a coefficientof chromaticity based on brightness of external light input as theenvironment information. The temperature coefficient setting unit 114 bsets a coefficient based on the temperature input as the environmentinformation. The chromaticity coefficient setting unit 114 c sets acoefficient based on chromaticity input as the environment information.The genre table 114 d sets a coefficient based on a genre of a videoinput as metadata. The user setting unit 114 e sets a coefficient basedon a genre of a video input as metadata. The user coefficient settingunit 112 e sets a coefficient based on a setting value set by the user.

The chromaticity calculation unit 114 f calculates optimal chromaticitybased on the coefficients set by the external light coefficient settingunit 114 a, the temperature coefficient setting unit 114 b, thechromaticity coefficient setting unit 114 c, the genre table 114 d, andthe user coefficient setting unit 114 e.

As described above, according to the brightness adjustment device 100 ofthe present embodiment, it becomes possible to adjust chromaticity ofvideo signal optically for each frame based on various conditions, suchas a user setting, environmental condition, or the like. Accordingly, itis possible to display optimal video according to various conditions bycontrolling peak brightness and power consumption respectively as wellas controlling chromaticity optimally.

[7. Process Procedure of Method of Adjusting Brightness]

Next, a process performed by the brightness adjustment device 100 willbe described. FIG. 7 is a flowchart illustrating a process performed bythe brightness adjustment device 100. First, in step S10, the settingcondition acquisition unit 108 acquires various setting conditions. Insubsequent step S12, the current-brightness control table 110individually sets the peak brightness and the power consumption based onthe various setting conditions and calculates the table illustrated inFIG. 2. The calculated table is to be stored as the current-brightnesscontrol table 110.

In subsequent step S14, chromaticity of video signal is calculated basedon various setting conditions by the chromaticity calculation unit 114.In subsequent step S16, the video frame of each frame is stored in thevideo signal memory 102. In subsequent step S18, the video-averagebrightness conversion block 104 calculates the average brightness ofeach frame by averaging brightness of all pixels of the video signal ofeach frame stored in the video signal memory 102.

In subsequent step S20, the average brightness calculated in step S18 isinput to the current-brightness control table 110, and the video gain iscalculated from the average brightness. In subsequent step S22, thevideo signal of each frame stored in the video signal memory 102 istransmitted to the video gain block 104 and multiplied by the video gaincalculated in step S20. In subsequent step S24, the video signalmultiplied by the video gain is sent to the chromaticity setting unit116, and chromaticity of the video signal is set to chromaticitycalculated in step S14.

The above described process may be performed by recording a computerprogram previously created to execute a corresponding process in arecording medium inside the display device and causing an arithmeticdevice (for example, a CPU) to sequentially read and execute thecorresponding computer program.

[8. Application of Backlight Device]

Next, an embodiment in which the present invention is applied to abacklight device will be described. The above described example has beendescribed in connection with the brightness adjustment device 100 of thedisplay device 200 including the organic EL panel that is configured toindividually control the peak brightness and the power consumption.However, a backlight device used in a liquid crystal display device orthe like may be configured by a similar configuration. FIG. 8 is afunctional block diagram illustrating a configuration of a displaydevice 1000 including a backlight device. In FIG. 8, the backlightdevice 1000 is configured with a liquid crystal display device.

As illustrated in FIG. 8, the display device 1000 includes a displaypanel 1200 that includes a color filter substrate, a liquid crystallayer, and the like, a surface light source 1300 disposed on a back sideof the display panel 1200, a control unit 1400 that controls the displaypanel 1200 and the surface light source 1300, and a power supply unit1410. The control unit 1400 and the power supply unit 1410 may beconfigured integrally with the display device 1100 or may be configuredseparately from the display device 1100.

The display device 1100 displays an original image corresponding to animage signal on a predetermined display area (an area corresponding to adisplay unit 1202 of the display panel 1200). For example, an inputimage signal input to the display device 1100 corresponds to an image (aframe image) of a frame rate of 60 Hz.

The display panel 1200 includes the display unit 1202 in which aplurality of opening sections through which white light from the surfacelight source 1300 is passed are arranged. The display panel 1200includes a source driver 1204 and a gate driver 1206 that transmit adriving signal to transistors (thin film transistors (TFTs) disposed inthe opening sections of the display unit 1202.

The white light that has passed through the opening sections of thedisplay unit 1202 is converted to red, green, or blue light by a colorfilter formed on the color filter substrate (not shown). A set includingthree opening sections that emit red, green, and blue light correspondsto one pixel of the display unit 1202.

The surface light source 1300 emits the white light in a light-emittingarea corresponding to the display unit 1202. The light-emitting area ofthe surface light source 1300 is divided into a plurality of blocks(areas), and light emission is controlled individually on each of theplurality of divided blocks.

The control unit 1400 includes a display brightness calculation unit1402, a light source control unit 1404, and a display panel control unit1406. An image signal corresponding to each frame image is supplied tothe display brightness calculation unit 1402. The display brightnesscalculation unit 1402 obtains a brightness distribution of a frame imagefrom the supplied image signal and calculates display brightnessnecessary for each block from the brightness distribution of the frameimage. The calculated display brightness is supplied to the light sourcecontrol unit 1404 and the display panel control unit 1406.

The light source control unit 1404 calculates backlight brightness ineach block of the surface light source 1300 based on the displaybrightness of each block supplied from the display brightnesscalculation unit 402. The light source control unit 1404 controls alight emission amount of a light-emitting diode (LED) 1330 of each blockin order to satisfy the calculated backlight brightness through pulsewidth modulation (PWM) control. Since the light-emitting brightness ofthe surface light source 1300 can be controlled for each block accordingto the input image signal as described above, optimal light emissionaccording to an image displayed on the display panel 1200 can beperformed. In some cases, controlling the light emitting brightness ofthe surface light source 1300 for each block according to the inputimage signal is called divided light-emitting driving or partiallight-emitting driving.

The light source control unit 1404 performs light-emitting control forperforming correction of light-emitting brightness or chromaticity basedon light-emitting brightness or chromaticity of each block detected by asensor disposed inside the backlight 1300. Here, the sensor includes anilluminance sensor, a color sensor, or the like.

The backlight brightness of each block of the surface light source 1300calculated by the light source control unit 1404 is supplied to thedisplay panel control unit 1406. The display panel control unit 1406calculates a liquid crystal aperture ratio of each pixel of the displayunit 1202 based on the display brightness of each block supplied fromthe display brightness calculation unit 1402 and the backlightbrightness of each block supplied from the light source control unit1404. In order to satisfy the calculated light crystal aperture ratio,the display panel control unit 1406 supplies a driving signal to thesource driver 1204 and the gate driver 1206 of the display panel 200 anddriving-controls the TFT of each pixel of the display unit 202. Thepower supply unit 1410 supplies each part of the display device 100 withpredetermined electric power.

FIG. 9 is a schematic diagram illustrating a configuration of abacklight device 1500 that includes the light source control unit 1404and the surface light source 1300. The light source control unit 1404has a configuration similar to the brightness control device 100 thathas been described with reference to FIG. 1. That is, the light sourcecontrol unit 1404 includes a memory 102, a gain block 104, an averagebrightness conversion block 106, and a setting condition acquisitionunit 108. The brightness adjustment device 100 further includes acurrent-brightness control table 110. Each of the functional blocksillustrated in FIG. 9 may be configured by hardware (a circuit) or anarithmetic processing unit (CPU) and software (a program) for causing itto function. When each functional block is configured by the arithmeticprocessing unit and the software, the program may be stored in a memoryincluded in the display device 200 or a recording medium such as amemory inserted from the outside.

The backlight brightness in each block of the surface light source 1300,which is calculated by the light source control unit 140, is input tothe memory 102. The video-average brightness conversion block 104calculates an average brightness of each frame by averaging brightnessof each block on a brightness signal of each frame. The calculatedaverage brightness is transmitted to the current-brightness controltable 110. The brightness signal is transmitted to the video gain block104 for each frame.

The current-brightness control table 110 retains a table in which arelationship between an average brightness and a gain is defined. Thecurrent-brightness control table 110 is a table for converting a gainamount by which the video signal is multiplied from an averagebrightness (an average video signal level) obtained from the videosignal for controlling a maximum brightness or a current value basedthereon. This table is created by the current-brightness tablecalculation unit 112 according to various conditions.

The current-brightness control table 110 calculates the video gain basedon the average brightness transmitted from the video-average brightnessconversion block 104 using the created table. The calculated video gainis transmitted to the video gain block 104.

The gain block 104 multiplies the corresponding brightness signal inputfrom the memory 102 by the gain calculated by the current-brightnesscontrol table 110. As a result, the brightness of the surface lightsource 1300 is optimally adjusted.

As described above, in the backlight device 1500, such as a liquidcrystal display device or the like, when the gain is adjusted based onthe brightness signal, it is possible to control peak brightness andpower consumption respectively.

The preferred embodiments of the present invention have been describedabove with reference to the accompanying drawings, whilst the presentinvention is not limited to the above examples, of course. A personskilled in the art may find various alternations and modificationswithin the scope of the appended claims, and it should be understoodthat they will naturally come under the technical scope of the presentinvention.

INDUSTRIAL APPLICABILITY

The present invention can broadly be applied, for example, to a displaydevice used in a television receiver or the like.

REFERENCE SIGNS LIST

-   100 Brightness adjustment device-   104 Video gain block-   106 Video-average brightness conversion block-   108 Setting condition acquisition unit-   110 Current-brightness control table-   112 Current-brightness table calculation unit-   114 Flash control calculation unit-   200 Display device-   300 Display panel

The invention claimed is:
 1. A display device, comprising: circuitryconfigured to acquire various conditions for adjusting a gain of a videosignal; calculate a table representing a relationship between an averagebrightness and the gain of the video signal, and calculate the tablecapable of setting a peak brightness and power consumption of the videosignal independently, based on the various conditions; calculate anaverage brightness of the video signal for each frame; a calculate thegain of the video signal from the table based on the average brightness;and adjust the video signal using the calculated gain; and a displaypanel that includes a plurality of pixels that emit light in response tothe video signal and displays a video based on the video signal adjustedby the circuitry.
 2. The display device according to claim 1, whereinthe circuitry is configured to acquire the various conditions includingenvironmental information indicating an environment surrounding thedisplay device, user setting information set by a user, information onmaximum power consumption that the display panel allows, or informationon meta data indicating a category of the video.
 3. The display deviceaccording to claim 1, wherein the circuitry comprises a memory whichholds temporarily a frame by which the gain is multiplied.
 4. Thedisplay device according to claim 1, wherein the circuitry is furtherconfigured to: calculate chromaticity of the video signal based on thevarious conditions; and adjust the chromaticity of the video signalusing the chromaticity calculated by the circuitry.
 5. A brightnessadjustment device, comprising: circuitry configured to acquire variousconditions for adjusting a gain of a video signal; calculate a tablerepresenting a relationship between an average brightness and the gainof the video signal, and calculate the table capable of setting a peakbrightness and power consumption of the video signal independently,based on the various conditions; calculate an average brightness of thevideo signal input for each frame; calculate the gain of the videosignal from the table based on the average; and adjust the video signalusing the calculated gain.
 6. The brightness adjustment device accordingto claim 5, wherein the circuitry is configured to acquire the variousconditions including environmental information indicating an environmentsurrounding the display device, user setting information set by a user,information on maximum power consumption that a display panel allows, orinformation on meta data indicating a category of a video.
 7. Thebrightness adjustment device according to claim 5, wherein the circuitrycomprises a memory which holds temporarily a frame by which the gain ismultiplied.
 8. The brightness adjustment device according to claim 5,wherein the circuitry is further configured to: calculate chromaticityof the video signal based on the various conditions; and adjustchromaticity of the video signal using the chromaticity calculated bythe circuitry.
 9. A method of adjusting brightness, comprising the stepsof: acquiring various conditions for adjusting a gain of a video signal;calculating a table representing a relationship between an averagebrightness and the gain of the video signal, and calculating the tablecapable of setting a peak brightness and power consumption of the videosignal independently, based on the various conditions; calculating anaverage brightness of the video signal for each frame; calculating thegain of a video signal from the table based on the calculated averagebrightness; and adjusting the video signal using the calculated gain.10. A non-transitory computer-readable medium storing instructions that,when executed on a computer, cause the computer to execute the steps of:acquiring various conditions for adjusting a gain of a video signal;calculating a table representing a relationship between an averagebrightness and the gain of the video signal, and calculating the tablecapable of setting a peak brightness and power consumption of the videosignal independently, based on the various conditions; calculating anaverage brightness of the video signal input for each frame; calculatingthe gain of the video signal from the table based on the calculatedaverage brightness; and adjusting the video signal using the calculatedgain.